This invention pertains to improvements in fluid transfer pumps, and more particularly to a new form of pump impeller and the method of manufacturing such devices.
A number of different types of fluid-handling pumps are known. This invention is concerned primarily with those types of pumps that employ rotating impellers, and particularly with those wherein the impeller is provided with elastomeric blades. Typical of such pumps are positive-displacement flexible-vane pumps. Such pumps consist of a pump housing and an impeller in the form of an eccentrically mounted rotor provided with a plurality of resiliently deformable vanes dimensioned to contact the interior wall of the pump housing. The impeller is preloaded in flexure within the pump housing to provide a movable seal between the impeller and the housing, thereby insuring efficient fluid transfer through a "wiper" action: resilient deformation of the vanes by the pump housing results in an eccentrically distributed volume between impeller and housing, and rotation of the impeller provides a positive displacement of the fluid. Inasmuch as the impeller vanes must flex (so as to act as a seal between the impeller and the housing) while the core portion of the impeller must be substantially rigid (so as to provide necessary structural attachment to a shaft), such impellers fabricated from a single material are at best a compromise. Typically, therefore, flexible-vane impellers are fabricated with a metal core, keyed as necessary to engage a shaft, to which are bonded a plurality of elastomeric vanes.
A number of problems arise from the structure of such pump impellers. Thus, for instance, the fabrication of such an impeller requires molding or fitting and otherwise bonding the vanes onto a separately fabricated (generally, cast and machined) metallic core. Typically, the core must be cleaned and treated with bond conditioner prior to the application of the vanes, and the latter, if molded onto the core, require that the temperature be carefully controlled through the curing cycle. Consequently, this manufacturing procedure requires a number of different steps, with an attendant impact on the cost of the item. It will be recognized that failure to properly execute these steps may further result in a poor bond between core and vanes. Additionally, when pumps using such prior art impellers are used to handle corrosive fluids, the metallic core, although in large measure isolated from the fluid by the surrounding elastomeric vanes, is not completely isolated, and consequently some corrosion of the core may occur.